Devices that include rotatable members may employ resolvers to monitor rotational position and rotational speed of the rotor. By way of non-limiting examples, powertrain systems may employ electrically-powered torque machines to generate tractive torque for propulsion. Known torque machines include multiphase electric motor/generators that electrically couple to energy storage devices via high-voltage electric buses and inverter modules. Torque machines may use resolvers to monitor rotational position and rotational speed, and use such information for control and operation thereof.
A resolver is an electromechanical transducer that includes a rotor having an excitation winding that is coupled to the rotatable member and a stator having secondary windings that are coupled to a non-rotating member of the device, wherein electromagnetic coupling between the primary winding and the secondary windings varies with the rotational position of the rotor. The primary winding may be excited with a sinusoidal signal, which induces differential output signals in the secondary windings. The magnitude of the electrical coupling onto the secondary windings relates to the rotational position of the rotor relative to that of the stator and an attenuation factor known as the resolver transformation ratio. In certain embodiments, the resolver is a variable reluctance resolver, in which an excitation winding is disposed in the stator, and an airgap between the rotor and the stator is modulated on the rotor, which modulates the transformation ratio depending on the rotational position. The output signals from the secondary windings may be phase-shifted by 90 degrees of rotation with respect to each other as a result of the secondary windings being mechanically displaced by 90/PP degrees of mechanical rotation, wherein PP is the quantity of pole pairs of the resolver. Thus, electrical rotation is determined based upon mechanical rotation divided by a quantity of electrical pole pairs. The primary winding may be excited with a sine wave reference signal, which induces differential output signals on the secondary windings. The relationships between the resolver input and the differential output signals may be used to determine a sine and a cosine of the rotational angle of the rotor. Thus, the relationships between the resolver input signal and the resolver output signals may be analyzed to dynamically determine an angular position and rotational speed of the rotor, and thus the rotating member.
Known systems employing resolvers have resolver-to-digital conversion integrated circuit devices to process input signals from the resolver to generate rotational information that may be employed by a controller.